How do I set the default selection for a drop list?

I'm creating a drop list like this:

${NSD_CreateDropList} 5u 23u 90% 80u ""

  Pop $TimeZoneDropList

  

  ${NSD_CB_AddString} $TimeZoneDropList "US/Alaska"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Arizona"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Central"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Eastern"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Hawaii"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Mountain"

  ${NSD_CB_AddString} $TimeZoneDropList "US/Pacific"

How do I set the default selection for the drop list?

I tried this, but it didn't do anything:

${NSD_CreateDropList} 5u 23u 90% 80u "US/Eastern"

Use ${NSD_CB_SelectString} $TimeZoneDropList "US/Eastern" after you have added the items to the list.